Goal:
    z : Z  z0 : Z  H : (z <= z0)%Z  H0 : (z0 <= z)%Z
  ============================
   (Some z = Some z0)


DEBUG:Going to execute:
contradiction
Level 0: Backtrace:

Proof is not complete.
Level 0: Backtrace:

Proof is not complete.
Level 1: Backtrace:

Proof is not complete.
Level 0: Backtrace:

Proof is not complete.
Level 0: Backtrace:

Proof is not complete.